Process for treating cellulosic textiles with formaldehyde in vapor form



United States Patent Office 3,lt,3?3 Patented Oct. 27, 1964 3,154,373 PRES FUR TREATING CELLULGEsiC TEXTKLES WKTH EGRMALDEHYDE EN VAPOR FORM .lohn D. Guthrie, New Orleans, La., assignor to the United States of America as represented by the Secretary of Agriculture No Drawing. Fiied Apr. 2, 1962, filer. No. 184,609 3 Claims. (Cl. 8-]ll6.4) (Granted under Title 35, US. Code (1952), see. 266) A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to a process for imparting durable wrinkle resistance or so-called wash-wear properties to cellulosic textiles and to articles fabricated therefrom. More particularly, it provides a method especially suited to treating completed garments to give them wash-wear and other desirable properties. It provides a unique method for fixing ironed in smoothness, ironed in creases, gloss, or luster produced by calendering, and other mechanical efiects; making these durable to laundering. The process is also applicable to handkerchiefs, sliver, yarn, and tufted rug material. The cellulosic materials with which it is effective include cotton, nondelustered viscose rayon and Fortisan (a fiber made by deacetylation of acetate rayon).

The process consists of exposing the cellulosic textile material in a particular way to a low concentration of the vapor of formaldehyde containing a small concentration of a volatile strong acid catalyst. The acidic formaldehyde vapor of the required composition is obtained from an essentially new material, made by exposing paraforrnaldehyde powder to vapor from concentrated hydrochloric acid.

The preferred way of practicing the invention involves first preparing the required treating material by exposing paraformaldehyde powder in a closed container to the vapor evolved from concentrated hydrochloric acid. The HCl-paraformaldehyde product, which contains about 1 percent HCl by weight, is then placed in a closed, non-reactive container along with the textile material. In the case of fabric, it may be dusted with the HCl-paraformaldehyde powder and sealed between glass plates, but better uniformity and convenience of treatment is obtained by hanging the material in a lar e, non-reactive container provided with a motor driven paddle wheel stirrer, the HClparaformaldehyde being placed as a layer in trays in the bottom of the container. The temperature preferred is room temperature, to 38 C. The textile materials are left in the container until a swatch of test fabric, several of which are also hung in the container, shows the desired Wash-wear or crease recovery properties in hand crunipling tests, wet or dry. The textile material is then removed and washed, or it may be hung in air until the odor of formaldehyde has left it.

A unique feature of the invention is that it provides a method for imparting the desired wrinkle recovery or wash-wear properties at a very low content of formaldehyde. About 0.1 percent formaldehyde by weight introduced into cotton fabric by this method produces crease recovery angles of about 250 W-i-F, wet or dry, by the Monsanto test method. Previously employed processes for treating cotton textiles with formaldehyde require a formaldehyde content of 0.7 to 1.0 percent to produce comparable crease recovery angles.

The invention is further illustrated by the following examples:

Example 1 PREPARATION OF HCl PARAFORMALDEHYDE DUST Commercial paraformaldehyde powder, g., was placed in a 2 liter wide mouthed, screw-capped brown bottle. A 50 m1. beaker provided with a glass fabric wick and containing 20 ml. of concentrated hydrochloric acid (36 to 38 percent by weight HCl) was put in the bottle on top of the paraformaldehyde, the bottle was closed tightly and allowed to stand at room temperature for two to four days, usually three days. The beaker was then removed, the bottle closed at once and shaken well. Analysis of this dust by addition of standard sodium hydroxide solution to a weighed amount in dilute alcohol and back titration with standard hydrochloric acid after one hour, using methyl red, indicated an HCl content of about 0.9%. Some of this was probably loosely combined H01 as indicated by a very sluggish end point when direct titration with standard sodium hydroxide was tried.

Example 2 TREATMENT WITH VAPOR FROM HCl-PARA- FORMALDEHYDE DUST The polyethylene container used for the vapor treatments was a cylindrical barrel 32 inches high and 21.5 inches in diameter. The vapor in it was stirred by a copper paddle wheel mounted on a shaft passing through the side and driven by a variable speed motor. The barrel was provided with a Plexiglas cover held down by weights. Shirts or garments, carefully ironed, were suspended on plastic hangers. Fabrics or other materials were hung from nichrome wires across the top or fastened with tape to the overhanging flange of the barrel. The HCl-paraformaldehyde dust was distributed from the bottles from which it was prepared into two 7 /2" x 11 /2" polyethylene trays placed in the bottom of the barrel. About 100 g. of the dust was added to each tray. Temperature of the room was recorded from time to time, and in some cases humidity of the air was estimated. The adequacy of treatment was determined by removing test pieces of bleached broadcloth and giving them hand crumpling tests, wet and dry. Time to obtain the desired degree of treatment was 20 to 30 hours. After each run, the dust was returned to the original bottle and regenerated by exposure to hydrochloric acid. The dust weighed about 15 g. less after each run. After two or three runs, this Weight loss was replaced by addition of fresh paraformaldehyde.

In most of these treatments more than one fabric sample, and frequently a shirt or other garment, was in the barrel. The fabric load ranged from to 350 g., temperature 20 to 30 C., and relative humidity 40 to 60%. Time for removal of the samples was usually determined by dry and wet hand crumpling tests of pieces of bleached broadcloth included in most runs. The samples remained in the barrel for 15 to 100 hours, usually 20 to 30 hours. Variations in the formaldehyde content and fabric properties were probably due to the abovementioned variables and possibly to the trace constituents of the fabrics and garments having a neutralizing action toward hydrochloric acid and to the number of times the dust had been regenerated. Wrinkle recovery angles, wet or dry, of 280 to 300 W-l-F were obtained with bleached cotton fabrics at 0.48% formaldehyde, with a breaking strength loss of about 50%. Wrinkle recovery angles of about 270 W+F were obtained at about 0.2% formaldehyde with various bleached cotton fabrics, with a breaking strength loss of about 40%. Comparable losses were observed in tear strength, as is typical of most formaldehyde treatments.

Most of the fabric samples were washed for about 40 minutes in hot alkaline tap Water after treatment, and air dried. Washing was omitted for some of the samples. These samples were hung in the air until the odor of formaldehyde was gone, and were analyzed and tested several months later. The formaldehyde contents were lower than in the washed samples, probably due to the reverse catalytic action of the hydrochloric acid before it diffused from the unwashed samples. There may have been a slight decrease in wrinkle recovery angles, but strength retention was not significantly changed by omission of washing after treatment.

It was interesting to note that recovery angles, wet or dry, of 250 to 270 W+F were obtained at 0.08 to 0.14% formaldehyde. This is about one-seventh of the formaldehyde content required for comparable recovery angles in other processes for treating cotton fabrics with formaldehyde. A favorable range of formaldehyde content for wash-wear properties appears to be from 0.20 to 0.25%, although strength losses are about 40% in this range. It is also of interest to note that if 0.11% formaldehyde introduced by this vapor method is considered to be the lowest required for significant wash-wear properties, it may be calculated that not more than one crosslink per 160 anhydroglucose units was required for significant increases in wrinkle recovery. Examination by electron microscopy of ultra-thin sections swollen in cuene showed evidence of crosslinking throughout the body of the fiber and not just at the surface.

Dyeings with Direct Blue 4 GL showed marked dyeresist, especially at 0.48% formaldehyde content. Good dye-resist was also shown by samples containing 0.2% formaldehyde.

Conditioned regain values for the treated samples ranged from 6.2 to 6.5%, control samples from 6.0 to 6.2%. Water imbibition of printcloth treated 'to give a formaldehyde content of 0.44% was 19% in comparison with 34% for the untreated control fabric.

In order to determine how well the vapor from the HCl-paraformaldehyde penetrated fabrics and other materials, five 6" x 9" pieces of broadcloth A were piled together and sealed at the edges with tape. This five layered assembly was treated for 27 hours along with other sample, disassembled and washed. Formaldehyde contents of the pieces were 0.17, 0.19, 0.16, 0.18, 0.18%, respectively, indicating excellent penetration to the center sample. A piece of the same fabric exposed on both sides containtd 0.22% formaldehyde.

Example 3 TREATMENT OF VARIOUS TEXTILE MATERIALS Yarnrfifikeins of bleached cotton yarn, 12 8/ 3, were treated with the vapor to a formaldehyde content of 0.16% for the washed samples. The unwashed sample that was analyzed about three months later had a formaldehyde content of 0.08%. Breaking strength values, control value given last, were 3.0, 2.7, and 5.2 pounds, respectively; elongations at break were 8.5, 7.9, and 11.0%; and regain values were 6.7, 6.4, and 6.6%.

Sliver.Raw cotton sliver was treated with the vapor. Formaldehyde contents ranged from 0.02 to 0.11%, but duplicate analyses were in poor agreement due to nonuniformity. Samples that were washed after treatment tended toward higher values than unwashed samples analyzed several months later. The nonuniformity was also evident in dyeing tests with Direct Blue 4 GL, in which considerable, but nonuniform, dye-resist was shown. Bundle tests on the treated samples averaged about 16 g. per tex. but agreement of duplicates was poor due to nonuniformity. The untreated control sliver value was 21 g. per tex. There was some decrease in elongation at break and in permanent set as a result of the treatment. Observations indicated that the treated samples recovered more than the untreated when compacted in a beaker. The nonuniformity of treatment and the rather low formaldehyde values observed with raw sliver are believed to be due to the inactivating effect on the HCl catalyst of poorly distributed noncellulosic constituents of the sliver.

Fixing of glaze on calendered fabric.The vapor treatment was effective in fixing the glaze on a cotton printcloth that had been given a high gloss by friction calendering. This fabric was treated to give a formaldehyde content of 0.25%. It retained noticeable gloss after ten home-type launderings. The same fabric that was not treated with the vapor lost its gloss completely when laundered once. The wrinkle-recovery angles, wet and dry, were also much improved by the treatment and decreased only a small extent on laundering.

Cotton rug materiaL-A sample of yellow colored, cut pile cotton rug material, 6" x 10", with rubber backing was treated. The rather thick, heavy pile was carefully brushed before treatment. To insure an adequate treatment, the rug material was left in the barrel for four days. It was not washed, but was put on the floor, along with a control sample, near a busy doorway where these samples were walked on for 10 months. During this period they were vacuum cleaned several times. The pile of the treated sample packed less than that of the control sample and showed a more uniformity of surface. It appeared to dry faster in the tumble dryer than the control sample.

Shirts, blouses, and handkerchids-During the course of the investigations, 20 shirts were treated individually in the barrel along with miscellaneous fabric samples. Most of these shirts were white, shrink-proofed broadcloth and had fused collars. Some colored shirts were included. These shirts have been worn and laundered by various people. Most of the shirts showed fair to good wash-wear properties, and all were much smoother than control shirts after laundering and tumble drying. One shirt, along with a control shirt, has been worn and home laundered 22 times. No bleach was used and it was tumble dried, but not ironed. It was much smoother than the control but now required touch-up ironing after laundering. It shows some seam puckering and pebbling, but much less than the control shirts. The creases originally ironed into the sleeves were still present in the treated shirt. Another pair of shirts has been worn and sent 30 times to a commercial laundry. Due to the heavy ironing and starching, the treated shirt showed no advantage over the control when worn. However, when the shirts were home laundered and tumble dried after the tenth use, the treated shirt was much smoother than the control shirt. The creases originally ironed into the sleeves of the treated shirt were still present.

A Womans pleated blouse that was difficult to iron was treated. The user reported that only touch-up ironing was required after it had been treated. A number of cotton handkerchiefs were treated after careful ironing. They gave satisfactory service, remained smoother than the controls during use, and required little or no ironing after laundering.

Textile materials other than c0tt0n.A number of fabrics composed of fibers other than cotton, as well as blends of some of these with cotton, were exposed in the barrel. These included acetate rayon, delustered viscose rayon, Fortisan, wool, and blends of cotton with Fortisan, nylon and Dacron. Of these, only the Fortisan and cotton-Fortisan blend (plied yarns, x 92) showed improvement in wrinkle recovery or in appearance after washing. The inefiectiveness of the vapor treatment on viscose was probably due to the presence of the delustering agent which may have inactivated the hydrochloric acid catalyst, since an experiment with two viscose yarns that were not delustered gave formaldehyde contents of 0.46 and 0.77 percent in comparison with 0.37 percent for bleached cotton yarn treated at the same time.

i claim:

1. A process for treating a cellulosic textile material, selected from the group consisting of cotton, deacetylated acetate rayon, and undelustered viscose rayon, which process comprises exposing the cellulosic textile material in an inert closed container to the vapors from a composition containing about O.5% to 1.2% by Weight of HCl made by exposing paraformaldehyde to vapor from concentrated hydrochloric acid.

2. The process of claim 1 in which the temperature of treatment is 20 to 33 C. and the time of treatment is 15 to 100 hours.

container is continuously circulated.

References (Iited in the file of this patent UN ETED STATES PATENTS Schneider Sept. 21, 1909 Cushman Dec. 6, 1921 Peterson Apr. 17, 1945 Pfeffer Feb. 17, 1948 Weisberg May 18, 1948 Walker Dec. 14, 1948 MacLean Sept. 18, 1951 OTHER REFERENCES Guthrie: American Dyestuff Reporter, vol. 51, No. 14, 3. The process of claim 1 in which the vapor in the 1 pp. 31-36, July 9, 1962. 

1. A PROCESS FOR TREATING A CELLULOSIC TEXTILE MATERIAL, SELECTED FROM THE GROUP CONSISTING OF COTTON, DEACETYLATED ACETATE RAYON, AND UNDELUSTERED VISCOSE RAYON, WHICH PROCESS COMPRISES EXPOSING THE CELLULOSIC TEXTILE MATERIAL IN AN INERT CLOSED CONTAINER TO THE VAPORS FROM A COMPOSITION CONTAINING ABOUT 0.5% TO 1.2% BY WEIGHT OF HCL MADE BY EXPOSING PARAFORMALDEHYDE TO VAPOR FROM CONCENTRATED HYDROCHLORIC ACID. 